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Alvis Stalwart
|type= |is_vehicle=yes | length=6.36 m | width=2.62 m | height=2.31 m | weight=9 tonnes | suspension= 6 x 6 wheels | Performance= road speed 63 km (39.37 mph); fording amphibious | vehicle_range=824 | primary_armament= none | secondary_armament= none | armour= none | engine= Rolls Royce B81 MK 8B eight cylinder water-cooled 6.5 l petrol, | engine_developing 220 hp (164 kW) | pw_ratio= | crew=driver + 2 passengers }} The FV 620 Stalwart, informally known by servicemen as the "Stolly", is a high mobility amphibious military truck built by Alvis that served with the British Army. History The Stalwart was a private venture by Alvis that was adopted and entered service with the British Army in 1966 as a general transport truck in preference to the FV431, the load carrier variant of the FV430 series. It was one of the same line of vehicles that included the Alvis Saracen, Saladin and Salamander. The high mobility and amphibious capabilities were considered ideal for resupplying units in the field. Design The hull is the vehicle chassis, the engine is situated under the load deck in the rear of the hull and the gearboxes, differentials and transfer boxes forward of this. The load deck was open-topped with large drop down panels on either side. Waterproof seals ensured that these would not leak when in the water. The three man cab has the driver's position in the centre and a seat for a passenger either side. The cab can only be entered through roof hatches. The Stalwart could carry 5 tonnes of stores, or tow 10 tonnes. In the water it was driven by vectored thrust water-jet propulsion units at about 6 knots. The drive system including the all-wheel drive, multiple gearboxes and the water propulsion units was complex and needed a lot of maintenance. When the amphibious qualities become unnecessary, it was common for the water jets to be removed to reduce weight and maintenance. The Stalwart's impressive over-terrain capabilities came from the fact that the 6-wheel-drive system lacked differentials, using simple bevel gears to transmit drive. A centre mounted no-spin differential allowed a certain amount of slip between the two sets of wheels on each side of the vehicle on hard surfaces, but there was no allowance for rotational speed differences between front and rear. The centre no-spin unit allowed the wheels on either side of the vehicle with most grip to drive when off-road. This had the effect of making the vehicle appear to crab (move from side to side) when negotiating muddy conditions, thus making the Stalwart a true 6-wheel-drive vehicle, with 3 wheels locked together and turning at the same speed. However, this system caused 'wind up' in the transmission (inter-component stress) as all the wheels were forced to rotate at the same speed, which during cornering is impossible. This led to rapid wear and breakage of the bevel gear boxes if the vehicle was used on firm surfaces such as tarmac or concrete – in off-road conditions the natural 'slip' of a loose surface such as mud or gravel prevented 'wind up'. This problem is of special concern for modern-day enthusiast Stalwart owners – to get a vehicle to a show either requires moving it by low-loader or driving it on the road, risking damage to the transmission. Variants ;FV620 First model ;FV621 Stalwart Mk 1 ;FV622 Stalwart Mk 2 General Service. This had a 2-man crew although a 3rd seat could be fitted to the right of the driver as a field modification. Could also carry 38 fully equipped troops or the Gloster SARO Bulk Refuelling Pack as alternatives to the 5 Ton cargo. The jet drive units in all the Mk 2 variants were much more efficient, giving a claimed 9 knots. The most obvious visible difference is that the lower edges of the cab windows were now angled downwards rather than horizontal. This was to improve visibility at close-range, particularly when being marshalled by a banksman standing nearby. ;FV623 Stalwart Mk 2 Limber. An artillery ammunition supply vehicle. Extra seat in cab for crane operator plus 4 extra seats, and an ATLAS 3001/66 hydraulic crane was added to the cargo area. ;FV624 REME fitter's vehicle, based on the Mk 2 Stalwart. Two extra seats were added and a different crane from the FV623 variant. Stalwarts in the media *Captain Tankboy uses an Alvis Stalwart FV622 as his Battle Truck in the crazy Reality TV show, Tankboy. *A Stalwart FV623 Series 2 was featured in Children of Men. Stalwart in Children of men Preservation A few examples of the Stalwart have been bought by Private collectors of military vehicles after they were decommisioned by the army following the end of the Cold War and the withdrawl of the Abott Self Propelled Gun from front line service. A Stalwart was restored by the Salvage Squad a Channel 4 TV programe. Known examples See also *List of UK Military vehicles by FV number * Military vehicles * Alvis * Shows and Meets - some feature Military vehicle displays. References / sources Further reading *John L Rue Stout Strong and Sturdy: The Alvis Stalwart story (Konig Verlag, 1998) External links *Salvage Squad restoration report *Amphibious Vehicle database - Alvis Stalwart – technical details and photos Stalwart Category:Military trucks of the United Kingdom Category:Military vehicles 1960–1969 Category:Cold War armoured fighting vehicles of the United Kingdom Category:Amphibious military vehicles Category:Off-road vehicles Category:Six-wheeled vehicles Category:Trucks built in the United Kingdom